The present invention is related to a method of operating a wind turbine, in which a meteorological value is measured and, taking into account this measured value, a desired value for the turbine operation is preset, an operation condition is selected and/or a boundary condition is determined for the turbine operation, as well as to a wind turbine for carrying out this method.
The meteorological variable of central importance for the operation of a wind turbine is the wind speed. In known methods for the operation of a wind turbine, the wind speed is measured by a cup anemometer, for instance. It is also known to select an operation condition depending on the wind speed, by way of example, to shut down the wind turbine above a cut-out wind speed, for instance by adjusting the blade pitch angle to the feathered position.
It is also known to take into account other meteorological variables in the operation of wind turbines, for example the air pressure and the air temperature. Concerning this, the document DE 198 44 258 A1, the contents of which is incorporated herein by reference, proposes to measure the air density and to set the cut-out wind speed depending on the measured wind density. In particular, at a lower air density, a higher cut-out wind speed shall be used than at a higher air density. The cut-out wind speed is a boundary condition for the operation of a wind turbine and is determined depending on the air density.
This procedure is based on the known relation that the forces exerted by the wind, in particular the drag and lift forces, depend on the air density. In a simplified manner, for the occurring forces F holds:
                              F          =                                    1              2                        ⁢                          ρ              air                        ⁢                          Av              2                        ⁢                          c              w                                      ,                            (                  equation          ⁢                                          ⁢          1                )            wherein ρair designates the air density, A the area that is applicable for the force that is to be calculated, ν the wind speed and cW the so-called force coefficient.Also known is the relation
                    P        =                              1            2                    ⁢                      ρ            air                    ⁢                      Av            3                    ⁢                      c            p                                              (                  equation          ⁢                                          ⁢          2                )            for the power P of a wind turbine, wherein cp designates the power coefficient. In a general manner, both equations show the importance of the air density, which participates in the occurring forces as well as in the power of the wind turbine as a linear factor.
Starting from this, it is the objective of the present invention to optimize the operation of a wind turbine.